This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-180206, filed Jun. 15, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to an inspection stage. More specifically, the present invention relates to an inspection stage upon which a test sample can be inspected with high reliability and which provides a space-saving feature as the application of an unbalanced load to a chuck top during inspection hardly inclines the chuck top.
Conventionally, a wafer prober is widely used for inspecting a test sample such as an integrated circuit formed on a semiconductor wafer. For ease of explanation, the following description deals with the case where the test sample is an integrated circuit (hereafter referred to as the IC chip) formed on a semiconductor wafer (hereafter referred to as the wafer). The wafer prober comprises a loader chamber and a prober chamber. The loader chamber transports the semiconductor wafer and prealigns it. The prober chamber inspects electric characteristics of the wafer transported from the loader chamber. The prober chamber is provided with an inspection stage which holds the wafer and is movable in X, Y, and Z directions. Above the inspection stage, there is provided a probe card having a plurality of probes. Moving the inspection stage aligns the IC chip formed on the wafer to a plurality of probes of the probe card. Then, the inspection stage is raised to electrically contact the IC chip""s electrodes with the probes. In this state, the electrical characteristics of the IC chip are inspected.
In recent years, however, IC chip integration is rapidly increasing, drastically increasing the number of electrode pads for IC chips and therefore narrowing the pitches in an array of electrode pads.
This increases the number of IC chips measured by a single operation (same measurement count) and the number of probes on a probe card. During inspection, a needle load applied to the chuck top via the probe increases to several tens to 200 kg. When an IC chip formed on the periphery of a wafer is inspected, an unbalanced load of several tens to 200 kg is applied to the wafer. The unbalanced load slants the chuck top. This slant makes it difficult to let each electrode pad of the IC chip evenly contact the probe card, degrading the inspection reliability.
In Jpn. Pat. Appln. No. 11-64997, we proposed an inspection stage and an inspection apparatus which hardly inclines a chuck top, even under a large needle load. As shown in FIG. 5, the inspection stage comprises a chuck top 1, a Z base 2, an X stage 3, and a Y stage 4. A wafer is placed on the chuck top 1. The chuck top 1 is mounted on the approximately triangular Z base 2 which can move up and down. The X stage 3 holds the Z base 2 by allowing vertical movement and moves in the X direction. The Y stage 4 holds the X stage 3 by allowing movement in the X direction and moves in the Y direction. The Z base 2 is provided with three elevating mechanisms arranged so that they surround the chuck top 1. The elevating mechanisms 5 move the Z base 2 horizontally.
When an unbalanced load is applied to a wafer placed on the chuck top 1 during inspection, the inspection stage disperses the unbalanced load into the elevating mechanisms 5. Consequently, an inclination of the chuck top 1 is decreased drastically.
When the diameter of the wafer diameter exceeds 300 mm, however, the chuck top 1 on the inspection stage also becomes larger. For example, FIG. 6A shows the chuck top 1 corresponding to a wafer measuring 200 mm in diameter. FIG. 6B shows this chuck top 1 is changed to a diameter for wafers measuring 300 mm or more in diameter. As seen from this figure, the shaded edge portions protrude from the area formed by the central region between each of the elevating mechanisms 5. When a portion of an IC chip in the shaded portion is inspected, a needle load is applied to the shaded portion, slightly depressing this portion. By contrast, the opposite side to this shaded portion rises. As a result, the chuck top 1 slants, causing the problem of the conventional inspection stage.
To prevent the chuck top 1 from slanting, the Z base 2 needs to be made larger, as shown in FIG. 7 so that a large-diameter chuck top 1 fits in the Z base 2. The X stage 3 and the Y stage 4 also need to be enlarged.
The present invention has been made in consideration of the foregoing. It is therefore an object of the present invention to provide an inspection stage which need not be enlarged if a test sample is enlarged.
Another object of the present invention to provide an inspection stage which prevents a chuck top from slanting remarkably if a test sample is enlarged.
Still another object of the present invention to provide an inspection stage which can ensure inspection reliability if a test sample is enlarged.
According to the first aspect of the present invention, there is provided an inspection stage comprising: a chuck top on which a test sample is mounted; a vertically movable support for supporting the chuck top; a support elevating mechanism having four or more Z axes for supporting the support and four or more Z axis elevating mechanisms for elevating each Z axis; an X stage capable of movement in an X direction for mounting the support elevating mechanism; and a Y stage capable of movement in a Y direction for mounting the X stage.
In the inspection stage, the support is preferably rectangular.
In the inspection stage, the four or more Z axis elevating mechanisms are preferably positioned so that a test sample mounted on the chuck top is arranged inside the region between these mechanisms.
In the inspection stage, the support elevating mechanism preferably further comprises an elevating position controller for adjusting vertical positions of each Z axis.
In the inspection stage, the elevating position controller preferably further comprises: a slant detection mechanism for detecting the horizontality of the support; and a slant controller for adjusting vertical positions of each Z axis and controlling the horizontality of the support within a specified range based on levelness of the support detected by the detection mechanism.
This inspection stage preferably further comprises a Z axis guide mechanism mounted on a bottom face of a support for guiding vertical movement of the support in a Z direction.
In the inspection stage, the Z axis guide mechanism preferably comprises a cylinder provided on one of the support and the X stage; and a column provided in the other of the support and the stage and reciprocatively fit in the cylinder.
In the inspection stage, the Z axis guide mechanism preferably comprises: a column provided on the support; and a cylinder provided on the X stage, wherein the cylinder fits to the column in a vertically movable state; and the X stage has an opening for the column to bore when the column moves vertically.
Other objects and advantages of the present invention will become apparent from the specification to follow. Parts thereof will be obvious from the disclosure or will become obvious by implementing the present invention. The objects and advantages of the present invention will be achieved and obtained by means and combinations particularly pointed out hereinafter.